Among the conventionally-known vehicle fuel supply devices are ones which include a fuel filter within a fuel tank (for example, International Publication WO2004/072469). In the vehicle fuel supply device disclosed in WO2004/072469, the fuel filter is disposed substantially centrally on the bottom of the fuel tank, a fuel pump unit is disposed in a rear portion of the fuel tank, and the fuel filter and fuel pump unit are interconnected via a fuel pipe.
In cases where fuel, such as ethanol, having fine dust, is used, the fuel filter has to have a small filtering mesh or pore size (i.e., filtering fineness); in these cases, however, the fuel filter has to be replaced in a short cycle, which increases the number of times maintenance work is to be performed. Further, in cases where such a small-pore fuel filter is provided upstream of the fuel pump unit, and when an amount of fuel to be supplied has rapidly increased, e.g. at the time of acceleration of the vehicle, it would be difficult for a necessary amount of the fuel to be supplied because the fuel filter becomes a fuel flow resistance, thus, there arises a need to enhance the capability or performance of the fuel pump unit, which requires increased cost.
Further, there have been known fuel supply devices in which a filter case and a pressure regulator are provided integrally with each other (for example, Japanese Patent Application Laying-Open Publication No. 08-74710 (JP 08-74710). In the fuel supply device disclosed in JP 08-74710, a fuel filter includes: a casing having an inlet, an outlet and a recirculation port; a filter insert of a cylindrical shape disposed inside the casing; and a pressure regulator disposed inside the casing adjacent to the recirculation port. The filter insert has opposite end caps fitted in the casing and supported by a support pipe. The pressure regulator is disposed inside the filter insert, and fuel is filtered as it passes through the filter insert from the outside to the interior of the filter insert.
If an attempt is made to secure a great surface area of the filter insert for an increased filtering capability, the casing has to have an increased size. Further, because the filter insert requires the support pipe, functioning as a frame, and end caps, the fuel supply device requires a great number of component parts and thus requires high cost. Further, the pressure regulator within the casing is subjected to a spatial constraint due to the provision of the filter insert and support pipe, which results in an extremely limited layout freedom of the pressure regulator, fuel suction port, etc. Furthermore, if the pressure regulator is disposed near the recirculation port, an installable location of the recirculation port would be limited.
Furthermore, there have been known fuel filter structures containing a filter element made of non-woven fabric or the like (for example, Japanese Patent Application Laying-Open Publication No. 2003-148267 (JP 2003-148267 A). In the fuel filter structure disclosed in JP 2003-148267 A, a filter cartridge includes a bag-shaped filter element formed of a mesh, non-woven fabric or the like, and a mounting section provided integrally with the bag-shaped filter element. Connection port provided in the mounting section is connected to a suction port of a fuel pump. The bag-shaped filter element is fixed to the mounting section via a suction port member inserted in the element. The suction port member integrally has a frame member for retaining the bag-shaped filter element in an inflated shape.
In cases where a primary fuel filter having a small pore size is employed in a fuel system, such the one disclosed in JP 2003-148267 A, to filter fuel, such as ethanol fuel, having fine (particle) dust, clogging would easily occur in the primary fuel filter. If the surface area of the primary fuel filter is increased in order to extend the life of the primary fuel filter, the primary fuel filter would increase in size, which results in a limited layout freedom and increased cost. Further, because the above-mentioned filter cartridge includes the suction port member, mounting section and frame member in addition to the bag-shaped element, the cartridge would have a large overall size. With vehicles, such as motorcycles, of which there exists a considerable restriction in relation to an available layout space on the vehicle body, it is desirable to construct the fuel supply system in a compact size by use of a non-woven fabric filter that achieves a high filtering efficiency even with a small surface area.